an=(10.5+0.5*n)*|sin(nπ/2)|+(10+n/2)*|cos(nπ/2)| n为奇数时,sin(nπ/2)=1,-1,1,-1这样循环出现,取绝对值后,成为1,1,1,.同时,cos(nπ/2)=0.n为偶数时,sin(nπ/2)=0,cos(nπ/2)=1,-1,1,-1循环出现,取绝对值后为1,...